JPH0536617B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an air-fuel ratio control method, and particularly to an air-fuel ratio control method suitable for use in a vehicle internal combustion engine having an electronically controlled fuel injection device.

[Background of the invention]

Engine rotation speed NE detected by rotation speed sensor
and the intake pipe pressure detected by the intake pipe pressure sensor.
In an electronically controlled fuel injection system that calculates the basic fuel injection time TP based on PM, the final fuel injection The time τ is calculated, and the injection valve is opened for the final fuel injection time τ to inject fuel.

On the other hand, in this type of fuel injection control device, which uses a three-way catalytic converter to simultaneously remove CO, HC, and NOx from exhaust gas as a countermeasure against exhaust emissions, It is desired to control the fuel ratio to near the stoichiometric air-fuel ratio. Therefore, an oxygen sensor is installed in the exhaust passage, and under certain conditions, the feedback correction coefficient FAF is adjusted so that the air-fuel ratio becomes close to the stoichiometric air-fuel ratio based on the air-fuel ratio signal from the oxygen sensor.
is calculated to perform air-fuel ratio feedback control.

In an electronically controlled fuel injection system that performs air-fuel ratio feedback control, it compensates for differences in air-fuel ratio due to variations between parts, compensates for air-fuel ratio due to high-altitude driving, and compensates for air-fuel ratio differences due to changes in intake pipe pressure sensor etc. over time. In order to compensate for changes in the fuel ratio, the air-fuel ratio is learned under predetermined conditions during the feedback control to maintain the base air-fuel ratio at a predetermined value.

The final fuel injection time τ is determined, for example, by the following formula: τ=(TP+TAUG)×(1+KG)×FAF×K. Here, TAUG is the learning correction amount calculated when the intake throttle valve is fully closed (at idle), KG is the learning correction coefficient calculated when the intake throttle valve is not fully closed, and K is the learning correction coefficient calculated when the intake throttle valve is not fully closed. temperature,
This is a correction coefficient based on water temperature, acceleration state, etc.

Here, the feedback correction coefficient FAF is, for example, 1.02 if the air-fuel ratio signal indicates a lean state.
For example, if it indicates a rich state, it will be 0.97. The learning correction amount TAUG is based on multiple feedback correction coefficients calculated during idle.
If the average value FAFAV of FAF is smaller than, for example, 1.0, it is subtracted, and if the average value FAFAV of correction coefficient FAF is larger, for example, than 1.0, it is added. Similarly, the learning correction coefficient KG is the average value other than when idling.
If FAFAV is smaller than 1.0, it is subtracted, and if it is larger than 1.0, it is added.

On the other hand, when an air conditioner is attached to an internal combustion engine having such an electronically controlled fuel injection device, atmospheric air is introduced into the intake passage during idle to increase the engine speed (referred to as air conditioner idle up). There is. At this time, the pressure in the intake passage increases, and in the engine for which the basic fuel injection time TP is determined as described above, the basic fuel injection time TP becomes large.

Normally, the basic fuel injection time TP determined from the engine speed NE and the intake pipe pressure PM is determined by the excess air ratio λ=
1. However, the engine
In reality, due to variations in parts or usage conditions, λ cannot be exactly 1 in all rotation and load ranges. Therefore, generally, the air-fuel ratio tends to shift to the rich side or lean side when the air conditioner idles up.

Referring to Figure 1, when the air-fuel ratio shifts to the rich side as the air conditioner idle increases in response to the operation of the air conditioner, the feedback correction coefficient FAF becomes smaller than 1.0 overall, and this causes its average value FAFAV becomes less than 1.0,
As a result, the learning correction amount TAUG during idling is reduced.

Therefore, the learning correction amount TAUG learned while the air conditioner is operating at idle.
However, if this is reflected in the fuel calculation when the air conditioner is not operating during startup or idling, the air-fuel ratio will be on the lean side or rich side, and there is a risk that good starting performance and stable idling rotation may not be obtained. In addition, there is a problem in that the base air-fuel ratio varies depending on whether the air conditioner is activated or not.

[Object of the invention] The object of the invention is to operate an air conditioner,
The object of the present invention is to propose an air-fuel ratio control method that can learn the air-fuel ratio so that the base air-fuel ratio does not fluctuate due to non-operation.

[Structure of the invention]

The basic fuel injection time TP calculated according to the engine speed NE and the intake pipe pressure PM is at least
The air-fuel ratio is set to the rich side when the average value of the feedback correction coefficient FAF, which is calculated so that the air-fuel ratio becomes the stoichiometric air-fuel ratio under the specified feedback conditions, and the feedback correction coefficient FAF under the specified learning conditions is greater than the specified value. The final fuel injection time τ is calculated based on the calculated learning correction amount TAUG that should shift the air-fuel ratio to the lean side when the air-fuel ratio is less than a predetermined value, and the final fuel injection time τ is calculated according to this final fuel injection time τ. The air-fuel ratio control method for an internal combustion engine that drives a fuel injection valve is characterized in that calculation of the learning correction amount TAUG is prohibited when the air conditioner idles up in response to the operation of the air conditioner stationer during idle.

〔Effect of the invention〕

According to the present invention, learning of the idle learning correction amount TAUG is prohibited when the air conditioner idles up, so that fluctuations in the base air fuel ratio in other operating ranges due to fluctuations in the air fuel ratio accompanying the idle up of the air conditioner are prevented. It can be prevented.

〔Example〕

Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 2 shows an example of an electronically controlled fuel injection type internal combustion engine to which the present invention is applied.
Reference numeral 2 indicates an intake passage, 14 a combustion chamber, and 16 an exhaust passage. An intake pressure sensor 20 provided in a surge tank 24 downstream of the throttle valve 18 is connected to a control circuit 22 via a signal line l1, and generates a voltage according to intake pressure. The intake air temperature sensor 21 is provided in the intake passage 12 upstream of the throttle valve 18, is connected to the control circuit 22 via a signal line l2, and generates a voltage according to the intake air temperature.

Intake air whose flow rate is controlled by a throttle valve 18 that is linked to an accelerator pedal (not shown) is guided to the combustion chamber 14 of each cylinder via a surge tank 24 and an intake valve 25.

A fuel injection valve 26 is provided for each cylinder,
Opening and closing are controlled in response to electrical drive pulses supplied from the control circuit 22 via the signal line l3, and pressurized fuel sent from a fuel supply system (not shown) is fed into the intake passage 12 near the intake valve 25, that is, the intake air. Injects intermittently into the port. The exhaust gas after being combusted in the combustion chamber 14 is discharged into the atmosphere via the exhaust valve 28, the exhaust passage 16, and the three-way catalytic converter 30.

Crank angle sensors 34 and 36 are attached to the distributor 32 of the engine, and these sensors 34 and 36 are connected to the control circuit 22 via signal lines 14 and 15. These sensors 34 and 36 output pulse signals each time the crankshaft rotates 30 degrees and 360 degrees, respectively, and these pulse signals are supplied to the control circuit 22 via signal lines l4 and l5, respectively.

The distributor 32 is connected to an igniter 38, and the igniter 38 is connected to the control circuit 22 via a signal line l6.

Reference numeral 40 indicates an idle switch (LL switch) which is linked to the throttle valve 18 and is closed when the throttle valve 18 is fully closed.
It is connected to the control circuit 22 via.

The exhaust passage 16 outputs a signal responsive to the oxygen concentration in the exhaust gas, that is, a signal with two different values depending on whether the air-fuel ratio is on the lean side or rich side with respect to the stoichiometric air-fuel ratio. _O2 that generates the output voltage
A sensor 42 is provided, the output signal of which is connected to the signal line l.
8 to the control circuit 22. The three-way catalytic converter 30 is provided downstream of the O ₂ sensor 42 and simultaneously purifies three harmful components, HC, CO, and NOx, in the exhaust gas.

Further, reference numeral 44 detects the engine cooling water temperature,
This is a water temperature sensor that generates a voltage according to the temperature, and is attached to the cylinder block 46 and connected to the control circuit 22 via a signal line 19.

Reference numeral 48 denotes an air conditioner switch that activates or deactivates the air conditioner, and is connected to the control circuit 22 via a signal line l10. Reference numeral 50 designates an electromagnetic switching valve, which is opened when the air conditioner is operated at idle to introduce atmospheric air into the intake passage 12, and when the air conditioner is not operated or when the air conditioner is not idling. Closed when activated. This switching valve 5
0 is connected to the control circuit 22 via the signal line l11.

As shown in FIG. 3, the control circuit 22 includes a central processing unit (CPU) 22a that controls various devices;
It has a read-on memory (ROM) 22b in which various numerical values and programs are written in advance, a random access memory (RAM) 22c in which numerical values and flags for calculation processes are written in a predetermined area, and an analog multiplexer function, and can accept analog input signals. A/D converter (ADC) that converts to digital signals
22d, input/output interface (I/O) 22e to which various digital signals are input, input/output interface (I/O) 22f to which various digital signals are output, is supplied with power from the auxiliary power source and retains memory when the engine is stopped. It is composed of a backup memory (BU-RAM) 22g, and a bus line 22h to which each of these devices is connected.

The ROM 22b contains a main processing routine program, a program for calculating fuel injection time (pulse width), a program for calculating an air-fuel ratio feedback correction coefficient, a learning correction coefficient to be described later, and various other programs, as well as programs for calculating these calculations. Various necessary data are stored in advance.

Then, an intake pressure sensor 20, an intake temperature sensor 2
1. O ₂ sensor 42 and water temperature sensor 44 are A/D
It is connected to a converter 22d, and voltage signals S1, S2, S3, S4 from each sensor are sequentially converted into binary signals according to instructions from the CPU 22a.

A pulse signal S5 every 30 degrees of crank angle from the crank angle sensor 34, a pulse signal S6 every 360 degrees of crank angle from the crank angle sensor 36, an idle signal S7 from the idle switch 40, and an air conditioner signal S10 from the air conditioner switch 48. , are respectively taken into the control circuit 22 via the I/O 22e. A binary signal representing the engine speed is formed on the basis of the pulse signal S5;
and S6 cooperate to form a request signal for fuel injection pulse width calculation, an interrupt signal for starting fuel injection, a cylinder discrimination signal, and the like. Furthermore, it is determined based on the idle signal S7 whether the throttle valve 18 is substantially fully closed, and the operating state of the air conditioner is determined based on the air conditioner signal S10.

From the I/O 22f, a fuel injection signal S8 and an ignition signal S9 formed by various calculations are output to the fuel injection valves 26a to 26d and the igniter 38, respectively, and in response to the idle signal S7 and the air conditioner signal S10. A switching signal S11 is output to the switching valve 50.

The fuel injection time (injection amount) in the internal combustion engine configured as described above is determined, for example, as follows.

τ=(TP+TAUG)×(1+KG)×FAF×K Where, τ=Final fuel injection time TP=Basic fuel injection time FAF=Feedback correction coefficient TAUG=Learning correction amount KG=Learning correction coefficient K=Water temperature, intake temperature, etc. The basic fuel injection time TP is determined by reading from a predetermined table or by calculation based on the intake pipe pressure PM and the engine speed NE.

The feedback correction coefficient FAF is a value that increases the injection amount if it is determined that the air-fuel ratio is lean based on the air-fuel ratio signal S3 from the O ₂ sensor 42 under feedback control conditions, for example.
1.05, and if the air-fuel ratio is determined to be rich based on the air-fuel ratio signal S3, it will be a value that reduces the injection amount, for example 0.95, and if it is not under the feedback control condition, the correction coefficient FAF will be 1.0.

An example of the calculation procedure for the feedback correction coefficient FAF is shown in FIG.

In step P1, it is determined whether a feedback condition is satisfied. For example, if the engine water temperature THW is not in the starting state or increasing after starting,
The conditions for feedback control are met when the temperature is 50°C or higher and the power is not being increased. If the conditions for feedback control are not satisfied, step P2
Then, set the feedback correction coefficient FAF to 1.0 so that no feedback control is executed, and end this procedure. If the conditions are met, proceed to step P3
Proceed to. In step P3, the air-fuel ratio signal S3 is read. In step P4, a filter is applied to the voltage value represented by the air-fuel ratio signal S3 to form an air-fuel ratio lean-rich flag so that it becomes "1" when rich and "0" when lean. If it is "1", it is determined that the air-fuel ratio is too rich, and a procedure is executed to make the air-fuel ratio lean.

That is, in step P6, the flag CAFL is set to zero, and the process proceeds to step P7, where it is determined whether or not the flag CAFR is zero. When it first shifts to the over-concentrated side, a flag is displayed.
Since CAFR is zero, proceed to step P9, and RAM2
Subtract a predetermined value α1 from the correction coefficient FAF stored in 2b, and use the result as a new correction coefficient FAF.
shall be. In step P10, the flag CAFR is set to 1. Therefore, if excessive concentration is determined twice or more in succession in step P5, a negative determination is always made in step P7 that passes from the second time onwards, and in step P8, a predetermined value β1 is subtracted from the correction coefficient FAF,
The FAF calculation is completed using the result as a new correction coefficient FAF.

On the other hand, if the lean rich flag based on the voltage value represented by the signal S3 is "0" in step P5, it is determined that the air-fuel ratio is lean, and the procedure is executed to make the air-fuel ratio rich. That is, in step P11, set the flag CAFR to zero and proceed to step P12,
Determine whether the flag CAFL is zero. When shifting to the lean side for the first time, the flag CAFL is zero, so proceed to step P13 and set the correction coefficient FAF to a predetermined value α.
2 is added and the result is set as a new correction coefficient FAF. In step P14, the flag CAFL is set to 1. Therefore, if it is determined that it is diluted twice or more in succession in step P5, a negative determination is always made in step P12 that is passed from the second time onwards, and in step P15, a predetermined value β2 is added to the correction coefficient FAF, and the result is The FAF calculation is ended with as a new correction coefficient FAF.

Note that α1, α2, β1, and β2 in steps P8, P9, P13, and P15 are predetermined values.

The feedback correction coefficient FAF determined by this calculation means is shown in FIG. 5 together with the lean rich flag of the air-fuel ratio A/F, which is expressed by filtering the voltage value represented by the air-fuel ratio signal S3. Referring to this figure, when the air-fuel ratio switches from lean to rich or from rich to lean, the correction coefficient
FAF is skipped by α1 or α2, and if it remains lean, a predetermined number β1 is successively subtracted, and if it remains rich, a predetermined number β2 is successively added.

Next, an example of the calculation procedure for the learning control amount TAUG and the learning control correction coefficient KG is shown in FIG.

First, in step P21, it is determined whether the intake throttle valve 18 is fully closed or not based on whether the idle signal S7 output from the idle switch 40 is on. If the intake throttle valve 18 is fully closed and an affirmative determination is made, in step P22, for example, the engine speed NE is 1000 rpm or less, and
Determine whether the intake pressure PM is 200mmHg or more.
If an affirmative determination is made, the process proceeds to step P24 to perform learning control.

On the other hand, if the intake throttle valve 18 is not in a fully closed state and a negative determination is made in step P21, then in step P23, for example, the intake pipe pressure PM is 200 mmHg or more.
Determine whether it is below 500mmHg. If an affirmative determination is made, the process proceeds to step P24 to perform learning control.

If a negative determination is made in step P22 or P23, no learning control is performed.

Next, in step P24, it is determined whether the learning conditions are satisfied. For example, air-fuel ratio feedback control is in progress and the engine coolant temperature THW is
Learning occurs when the temperature is 80°C or higher and the intake air temperature THA is between 40°C and 90°C. If it is determined that the learning conditions are satisfied, the feedback correction coefficient is set in step P25.
It is determined whether the FAF has skipped or not, and if the skip is affirmatively determined, the process advances to step P26. Procedure P
25 is the flag CAFL mentioned above, CAFR is “1”
→ This is determined by the change to “0”. In step P26, the value of the correction coefficient FAF immediately before skipping is read, and in step P27, the correction coefficient FAFn read this time and the correction coefficient FAFn read last time are read.
-1 and the arithmetic average value FAFAV is determined and stored in a predetermined area. Next, in step P28, it is determined whether the arithmetic average value FAFAV is 1.0 or more. If the arithmetic mean value FAFAV is 1.0 or more, step P28-
1, it is determined whether the intake throttle valve 18 is fully closed, and if it is fully closed, the process advances to step P29. In step P29, the air conditioner is activated,
The non-operation is determined based on the air conditioner signal S10, and if the air conditioner is not operating, the learned correction amount is determined in step P30.
Add "2" to TAUG and use the result as a new learning correction amount TAUG. If the air conditioner is operating, the learning correction amount TAUG will not be learned. On the other hand, if the intake valve throttle valve 18 is not fully closed, proceed to step P31, add "0.005" to the learning correction coefficient KG, and use the result as a new correction coefficient.
KG.

If the arithmetic mean value FAFAV is less than 1.0, procedure P
In step 28-2, it is determined whether the intake throttle valve 18 is fully closed, and if it is fully closed, the process advances to step P32. In step P32, it is determined whether the air conditioner is activated or not, and if it is not activated, in step P33, "2" is set from the learning correction amount TAUG.
and use the result as the new learning control amount TAUG
shall be. If the air conditioner is operating, the learning correction amount TAUG will not be learned. On the other hand, if the intake throttle valve 18 is not fully closed, the process proceeds to step P34, where "0.005" is subtracted from the learning correction coefficient KG, and the result is set as a new correction coefficient KG.

In this way, in this embodiment, the learning correction amount
The air-fuel ratio when the intake throttle valve 18 is fully closed is learned by TAUG, and the air-fuel ratio when the intake throttle valve 18 is open is learned by the learning control correction coefficient KG. Learning is not performed when idle up is being performed, thereby preventing fluctuations in the base air-fuel ratio.

[Modified example]

The invention can be applied to any type of air conditioner in which the basic fuel injection time TP is determined based on the engine speed NE and the intake pressure PM, and the air conditioner idle is increased.

[Brief explanation of the drawing]

Figure 1 shows the air-fuel ratio, FAF average value FAFAV, and learning correction amount as the air conditioner turns on and off.
A time chart showing fluctuations in TAUG, engine speed NE, and intake pipe pressure PM. Fig. 2 is a configuration example showing an example of an internal combustion engine having an electronically controlled fuel injection device to which the method of the present invention is applied. Fig. 3 is an example of the configuration. A block diagram showing a detailed example of the control circuit, Fig. 4 is a flowchart showing an example of the procedure of the FAF calculation routine, Fig. 5 is a time chart showing the lean rich flag and correction coefficient FAF, and Fig. 6 is the TAUG and KG calculation routine. This is a flowchart showing an example of the procedure. 10... Engine body, 12... Intake passage, 18...
...Intake throttle valve, 20...Intake pipe pressure sensor, 22
... Control circuit, 26 ... Injection valve, 34, 36 ...
Crank angle sensor, 40...Idle switch,
42...O ₂ sensor, 48...Air conditioner switch,
50...Switching valve.

Claims (1)

[Claims] 1. The basic fuel injection time TP calculated according to the engine speed NE and the intake pipe pressure PM is at least
The air-fuel ratio is set to the rich side when the average value of the feedback correction coefficient FAF, which is calculated so that the air-fuel ratio becomes the stoichiometric air-fuel ratio under the specified feedback conditions, and the feedback correction coefficient FAF under the specified learning conditions is greater than the specified value. The final fuel injection time τ is calculated based on the calculated learning correction amount TAUG that should shift the air-fuel ratio to the lean side when the air-fuel ratio is less than a predetermined value, and the final fuel injection time τ is calculated according to this final fuel injection time τ. An air-fuel ratio control method for an internal combustion engine that drives a fuel injection valve, characterized in that calculation of the learned correction amount TAUG is prohibited when the air conditioner idles up in response to the operation of an air conditioner stationer during idle. Fuel ratio control method.